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概述：本文主要讲解了flutter网络请求三种方式 flutter自带的HttpClient、 第三方库http 和 第三方库Dio 的简单实现 GET 和 POST请求，本文是笔者学习Flutter网络模块知识总结，若有问题还望不腻赐教。

一、系统自带HttpClient

1、使用中温馨提示

1.1、导入库

import 'dart:io'; // 网络请求
import 'dart:convert'; // 数据解析

1.2、Uri的多种初始化方式

// 方法1
Uri uri = Uri(scheme: 'https', host: 'xxx.xxx.xxx.xxx', path: homeNoviceListUrl);
// 方法2
Uri uri = Uri.https('xxx.xxx.xxx.xxx', homeNoviceListUrl);
// uri方法3
Uri uri = Uri.parse(njqbaseUrl + homeNoviceListUrl);

2、简单使用

2.1、GET请求

// 1.1 HttpClient - get （疑问？queryParameters仅仅用在get请求吗）
void loadData_sys_get() async {
print('------loadData_sys_get--------');

var httpClient = new HttpClient();
var params = Map<String, String>();

// uri方法1
Uri uri =
    Uri(scheme: 'https', host: 'xxx.xxx.xxx.xxx', path: homeNoviceListUrl);

// uri方法2
// Uri uri = Uri.https(
//     'xxx.xxx.xxx.xxx', homeNoviceListUrl);

// uri方法3
// Uri uri = Uri.parse(njqbaseUrl + homeNoviceListUrl);

var request = await httpClient.getUrl(uri);

var headers = Map<String, String>();
headers['loginSource'] = 'IOS';
headers['useVersion'] = '3.1.0';
headers['isEncoded'] = '1';
headers['bundleId'] = 'com.nongfadai.iospro';

request.headers.add("loginSource", "IOS");
request.headers.add("useVersion", "3.1.0");
request.headers.add("isEncoded", "1");
request.headers.add("bundleId", "com.nongfadai.iospro");

var response = await request.close();
var responseBody = await response.transform(Utf8Decoder()).join();

if (response.statusCode == HttpStatus.ok) {
  print('请求头：${response.headers}');

  print('111请求成功代发数据为:\n $responseBody');
  print('--------------');
  Map data = jsonDecode(responseBody);
  print('222请求成功代发数据为:\n $data');
} else {
  print('\n\n\n11111==请求失败${response.statusCode}');
}
}

2.2.POST请求

注意点：请求参数需要编码后放在request中

void loadData_sys_post() async {
print('------loadData_sys_post--------');

HttpClient httpClient = new HttpClient();

// queryParameters get请求的查询参数(适用于get请求？？？是吗？？？)
// Uri uri = Uri(
//     scheme: "https", host: "xxx.xxx.xxx.xxx", path: homeRegularListUrl);
// HttpClientRequest request = await httpClient.postUrl(uri);

var url = njqbaseUrl + homeRegularListUrl;
HttpClientRequest request = await httpClient.postUrl(Uri.parse(url));

// 设置请求头
request.headers.set("loginSource", "IOS");
request.headers.set("useVersion", "3.1.0");
request.headers.set("isEncoded", "1");
request.headers.set("bundleId", "com.nongfadai.iospro");
// Content-Type大小写都ok
request.headers.set('content-type', 'application/json');

/// 添加请求体
/// https://stackoverflow.com/questions/50278258/http-post-with-json-on-body-flutter-dart/50295533
Map jsonMap = {'currentPage': '1'};
request.add(utf8.encode(json.encode(jsonMap)));

HttpClientResponse response = await request.close();
String responseBody = await response.transform(utf8.decoder).join();
if (response.statusCode == HttpStatus.ok) {
  print('请求成功');
  print(response.headers);
  print(responseBody);
}
}

二、请求第三方库 http

1、使用中温馨提示

1.1、添加依赖

dependencies:
  http: ^0.12.0 #latest version

1.2、导入库

import 'package:http/http.dart' as http; //导入前需要配置

2、简单使用

2.1. GET请求

2.2.1. http - get1

  void loadData_http_get() async {
    print('------loadData_http_get--------');

    var client = http.Client();

    var uri = Uri.parse(njqbaseUrl + homeNoviceListUrl);

    http.Response response = await client.get(uri);

    if (response.statusCode == HttpStatus.ok) {
      print(response.body);
    } else {
      print('请求失败 code 码为${response.statusCode}');
    }
  }

1.2. http - get简便方法（链式编程）

void loadData_http_get_convenience() async {
    print('------简便方法loadData_http_get_convenience--------');

    var uri = Uri.parse(njqbaseUrl + homeNoviceListUrl);

    http.Client().get(uri).then((http.Response response) {
      if (response.statusCode == HttpStatus.ok) {
        print(response.body);
      } else {
        print('请求失败 code 码为${response.statusCode}');
      }
    });
  }

2.2. POST请求

2.2.1. http - post

  void loadData_http_post() async {
    print('------ loadData_http_post --------');

    var headers = Map<String, String>();
    headers["loginSource"] = "IOS";
    headers["useVersion"] = "3.1.0";
    headers["isEncoded"] = "1";
    headers["bundleId"] = "com.nongfadai.iospro";
    headers["loginSource"] = "IOS";
    headers["Content\-Type"] = "application/json";

    Map params = {'currentPage': '1'};
    // 嵌套两层都可以，但是具体哪个好还有待确认？？？？
    var jsonParams = utf8.encode(json.encode(params));
    // var jsonParams = json.encode(params);

    var httpClient = http.Client();

    var uri = Uri.parse(njqbaseUrl + homeNoviceListUrl);

    http.Response response =
        await httpClient.post(uri, body: jsonParams, headers: headers);

    if (response.statusCode == HttpStatus.ok) {
      print(response.body);
    } else {
      print('请求失败 code 码���${response.statusCode}');
    }
  }

2.2.2. http - Post简便方法（链式编程）

  void loadData_http_post_convenience() async {
    print('------ loadData_http_post --------');

    var headers = Map<String, String>();
    headers["loginSource"] = "IOS";
    headers["useVersion"] = "3.1.0";
    headers["isEncoded"] = "1";
    headers["bundleId"] = "com.nongfadai.iospro";
    headers["loginSource"] = "IOS";
    headers["Content\-Type"] = "application/json";

    Map params = {'currentPage': '1'};
    // 嵌套两层都可以，但是具体哪个好还有待确认？？？？
    var jsonParams = utf8.encode(json.encode(params));
    // var jsonParams = json.encode(params);

    var httpClient = http.Client();

    var url = njqbaseUrl + homeRegularListUrl;

    httpClient.post(url, body: jsonParams, headers: headers).then((response) {
      print("Response status: ${response.statusCode}");
      print("Response body: ${response.body}");
    }).whenComplete(httpClient.close);
  }

三、请求第三方库 Dio

1、使用中温馨提示

1.1、添加依赖

dependencies:
  dio: ^2.0.11 #latest version

1.2、导入库

import 'package:dio/dio.dart';

2、简单使用

2.1. GET请求

注意：
dio的get请求（baseUrl都是在dio.option.baseUrl设置的）
请求头可以在dio.option上设置，也可以在新建的option上设置,新建option是可选的

void loadData_dio_get() async {
    var headers = Map<String, String>();
    headers['loginSource'] = 'IOS';
    headers['useVersion'] = '3.1.0';
    headers['isEncoded'] = '1';
    headers['bundleId'] = 'com.nongfadai.iospro';
    headers['Content-Type'] = 'application/json';

    Dio dio = Dio();
    dio.options.headers.addAll(headers);
    dio.options.baseUrl = njqbaseUrl;

    Response response = await dio.get(homeNoviceListUrl);

    if (response.statusCode == HttpStatus.ok) {
      print(response.headers);
      print(response.data);
    }
  }

2.2. POST请求

2.2.1 dio - 方式一（baseUrl都是在dio.option.baseUrl设置的）
注意：直接在 dio.options设置除methods以外的 请求头参数

void loadData_dio_dioOfOptionsSetting() async {
    debugPrint(
        ' \n post请求 ======================= 开始请求 =======================\n');
    var headers = Map<String, String>();
    headers['loginSource'] = 'IOS';
    headers['useVersion'] = '3.1.0';
    headers['isEncoded'] = '1';
    headers['bundleId'] = 'com.nongfadai.iospro';
    headers['Content-Type'] = 'application/json';

    Dio dio = Dio();
    dio.options.baseUrl = njqbaseUrl;
    dio.options.connectTimeout = 60000;
    dio.options.receiveTimeout = 60000;
    dio.options.headers.addAll(headers);
    dio.options.method = 'post';

    Options option = Options(method: 'post');
    // Response response = await dio.request(homeRegularListUrl,
    //     data: {"currentPage": "1"}, options: option);

    Response response = await dio.post(homeRegularListUrl,
        data: {"currentPage": "1"}, options: option);

    if (response.statusCode == HttpStatus.ok) {
      debugPrint('请求参数： ${response.request.queryParameters}');
      debugPrint(
          '-------------------请求成功,请求结果如下:-----------------\n \n===请求求url: ${response.request.uri.toString()} \n \n===请求 ���:   \n${response.headers} \n \n===请求结果: \n${response.data}\n');
      debugPrint('-------------------请求成功,请求结果打印完毕----------------');
    } else {
      print('请求失败');
    }
  }

2.2.2 dio - 方式二（baseUrl都是在dio.option.baseUrl设置的）
注意：在新建的option上设置请求头参数

void loadData_dio_newOptionSetting() async {
    debugPrint(' \n======================= 开始请求 =======================\n');
    var headers = Map<String, String>();
    headers['loginSource'] = 'IOS';
    headers['useVersion'] = '3.1.0';
    headers['isEncoded'] = '1';
    headers['bundleId'] = 'com.nongfadai.iospro';
    headers['Content-Type'] = 'application/json';

    Options option = Options(method: 'post');
    option.connectTimeout = 60000;
    option.receiveTimeout = 60000;
    option.headers.addAll(headers);

    Dio dio = Dio();
    dio.options.baseUrl = njqbaseUrl;

    Response response = await dio.post(homeRegularListUrl,
        data: {"currentPage": 1}, options: option);
    // Response response = await dio.request(homeRegularListUrl,
    // data: {"currentPage": 1}, options: option);

    if (response.statusCode == HttpStatus.ok) {
      debugPrint('请求参数： ${response.request.queryParameters}');
      debugPrint(
          '-------------------请求成功,请求结果如下:-----------------\n \n===请求url: ${response.request.uri.toString()} \n \n===请求 头:   \n${response.headers} \n \n===请求结果: \n${response.data}\n');
      debugPrint('-------------------请求成功,请求结果打印完毕----------------');
    } else {
      print('请求失败');
    }
  }